The ability to locate RF devices within a building has long been sought after. Attempts to locate laptops, for example, and tagged devices have been proposed wherein a plurality of wireless receivers each transmit a signal and then try to identify through triangulation, for example, a location of the RF signal source. In one such system, phased array antennas used for each of the wireless receivers allow them to determine angle of incidence of the RF signals. With two receivers, an accurate estimation of transmitter location is possible in a test environment. Unfortunately, in real world environments reflections and other signal distortions result in errors in the location determinations and as such, these systems are problematic in commercial applications.
More recently, RF fingerprinting has been studied wherein a receiver is in motion and transmitted signals received thereby are used to estimate location. It has been found that with one transmitter in a controlled environment, it is possible to accurately estimate location. Unfortunately, like the other prior art, real world applications have eluded this technology for many reasons. First, there is signal reliability issues where noise levels, reflections, interference, weather, speed, receiver battery levels, etc. all affect the results. Second, in highly controlled environments it is easier to assure uniqueness of a received RF signal at every point within the controlled space. Third, controlled environments are highly static whereas the commercial world is not. Fourth, in a controlled environment certain features are excluded as problematic whereas in a commercial application, someone does not want to hear that they need to replace all of their metal fixtures with plastic ones.
It would be advantageous to provide a method and system for supporting commercial indoor RF based location services.